如何在 dplyr 和 R 中汇总和子集多级分组数据帧

Question

我有以下长格式数据：

testdf <- tibble(
          name = c(rep("john", 4), rep("joe", 2)), 
          rep = c(1, 1, 2, 2, 1, 1), 
          field = rep(c("pet", "age"), 3), 
          value = c("dog", "young", "cat", "old", "fish", "young")
)

对于每个指定的人（约翰和乔），我想总结他们的每只宠物：
由于某种原因，我似乎无法处理“约翰”数据中的重复事件/宠物。
如果我只过滤乔（只有一只宠物），则代码有效。

任何帮助非常感谢...

testdf %>%
          group_by(name, rep) %>%
        #  filter(name == "joe") %>%  # when I filter only for Joe, the code works
          summarise(
                    about = paste0(
                              "The pet is a: ", .[field == "pet", "value"], " and it is ", .[field == "age", "value"]
                    )
          )

Answer 1

testdf %>%
  pivot_wider(id_cols = name:rep,names_from = field) %>% 
  mutate(about = paste0("The pet is a: ", pet, " and it is ", age))

  name    rep pet   age   about                             
  <chr> <dbl> <chr> <chr> <chr>                             
1 john      1 dog   young The pet is a: dog and it is young 
2 john      2 cat   old   The pet is a: cat and it is old   
3 joe       1 fish  young The pet is a: fish and it is young

这也可以通过 data.table 来完成，如下所示：

library(data.table)

setDT(testdf)[
  ,j = .(about = paste0("The pet is a ", .SD[field=="pet",value], " and it is ", .SD[field=="age",value])),
  by = .(name,rep)
]

   name rep                             about
1: john   1  The pet is a dog and it is young
2: john   2    The pet is a cat and it is old
3:  joe   1 The pet is a fish and it is young

Answer 2

您的数据格式较长且不整齐，其中包含多个字段。因此，郎唐回答的就是将其扩展或转向更广泛。 （更好的是使用 data.table，但我发现使用 .SD 仍然很困难]

我更喜欢在 dplyr 中尽可能简单地完成这些事情。
另一种不扩散的方法如下，它产生相同的结果。 [没有data.table其中.SD对我来说仍然很难掌握！
所以在 3 行中：

testdf%>%
  group_by(name,rep)%>%    
  summarise(about = paste("The pet is ",value[field=='pet']," and it is ",value[field=='age']))

产量：

      name    rep about                             
  <chr> <dbl> <chr>                             
1 joe       1 The pet is  fish  and it is  young
2 john      1 The pet is  dog  and it is  young 
3 john      2 The pet is  cat  and it is  old